The City of Calistoga is moving forward with developing a microgrid, but rather than designing it for disaster response, as many California communities plan to do, it will be used for citywide resilience.

The Clean Coalition on July 29 announced it had signed a consulting agreement to conduct a feasibility assessment for the city’s microgrid.

Public-safety power shut-offs planned by utilities to mitigate wildfire risk are the main concern, and city leaders and consultants want to design a project that provides area residents with resilience in light of possible distribution-line de-energizing during fire season.

“Our fundamental concern is the uncertainty with the PSPSes and the overall impact to the community,” Calistoga City Manager Michael Kirn said. Both residents and commercial entities need reassurance that their service is not going to be disrupted. The area’s economy is largely dependent on tourism.

Kirn said it is unclear how the system will interface with the existing Pacific Gas & Electric distribution system and an anticipated “resilience zone.” The concept had been for the microgrid to be located in a designated PG&E resilience zone with a grid interconnection that would enable a section of the grid to be islanded from the larger grid, enabling critical facilities to stay on line.

But PG&E told California Energy Markets that Calistoga is not a candidate for one of its resilience zones. The pilot program is currently only in Angwin, which is in Napa County as Calistoga is, according to PG&E spokesman Jeff Smith. It is not clear how that discrepancy will play out or affect the project.

The Calistoga microgrid project is still in the early planning stages, according to the Clean Coalition, which says stakeholder outreach to determine critical facilities and community needs is the next step.

Frank Wasko, managing director for the Clean Coalition, says the project is on a “fast track.” Within the next few weeks, the group will be conducting a technical analysis, which will include working with PG&E, local geothermal contacts and community choice aggregator MCE as well as the city “to understand where they want us to focus.”

“That will help tighten up our scoping process so that we can proceed with the system sizing and design,” Wasko said.

The Clean Coalition, based in Menlo Park, works to design and stage community microgrids in partnership with developers that are responsible for installing the microgrids. It is currently working on a microgrid in the Montecito community (see CEM No. 1529 [16]).

Much like the Montecito project, there will be a phased implementation in Calistoga starting with critical facilities. The assessment will initially identify candidate locations for five different microgrids. Some of these might include one or two of the nearby water-treatment plants, public schools, or the fire department. These facilities’ microgrids could potentially be connected into a full community microgrid serving the Calistoga Substation grid area as originally envisioned.

Electric-grid resilience is a key issue for communities and cities in areas where wildfires are a near and ever-present danger, but plans to shut down power lines during high-wind, high-fire-danger conditions are a concern. Even a single power shut-off could result in communities being without power for days, or even a week or more, during the fire season, Gov. Gavin Newsom said earlier this year. PG&E forecast that some areas—including Calistoga—could face outages 15 times a year.

This possibility is propelling local-government officials to investigate how microgrids can keep critical facilities operational. Fire stations, hospitals, water districts and other local facilities could be left without power, and a diesel backup generator might not be adequate.

The City of Calistoga had two PSPS warnings last fall, with one resulting in a shutoff. In May, a month of PG&E maintenance work necessitated the installation of diesel generators in the city as backup power. Another warning was issued to the city June 7, according to documents filed with the California Public Utilities Commission.

Wasko said the potential loss of business revenues from outages might require classifying tourist destinations, such as three large resorts in the area, as potential critical facilities. The assessment will also identify the at-risk population. The area has a lot of older residents who need uninterrupted power to address their ongoing health needs, Wasko said.

The Clean Coalition will also identify commercial-scale solar siting potential in Calistoga. Program engineer Malini Kannan said the organization might look at both solar plus storage and geothermal energy for use in the microgrids. As of 2015, the Calistoga area had 2.5 MW of distributed solar, she said. Half of that is residential installations and the other half nonresidential.

“This is unique,” said Wasko of the process. “We do plan to leave the door open for a community microgrid, to provide at least a framework for it to be connected with the existing distribution grid if the city wants that.” The focus now is “an immediate and prompt solution for the city and constituents who want to move forward quickly.”